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cathector sends along a story from SpaceWeather.com on the discovery of water ice on Mars.
"Scientists have figured out the mysterious white substance unearthed by NASA's Phoenix lander on Mars. It's frozen water. The breakthrough came last week when Phoenix's stereo camera caught the substance in the act of disappearing. Bathed in martian sunlight for four days, the white substance sublimated — i.e., it transformed from solid to gas without passing through the liquid state. This is how water behaves on Mars.... Some readers have asked, how do we know the white substance is not frozen CO2 (dry ice) instead of frozen water? Answer: Phoenix's landing site is too warm for dry ice. The average daily temperature is about -70 F while dry ice requires temperatures lower than about -109 F." The animated GIF showing the ice sublimating is pretty nice too.

So, if we sent a bunch of robot tractors to Mars and uncovered the dirty ice caps, wouldn't they all sublimate and all that water vapor would warm the planet? Are we looking at a cheap way to terraform the planet?

Actually, that argument can be made for any atmospheric gas constituent, not just water vapor.

There is less water in the Martian atmosphere oxygen while the water is more massive, so the oxygen would leave at a proportionally greater rate (assuming we are observing a long term steady state). One theory of the rapid loss has more to do with disassociation of H and O by UV radiation. H would quickly leave by your molecular motion argument leaving a relatively larger amount of O.

I would rather use the nukes to bring a few asteroids to impact mars. Some of those contain a load of ammonia. Ammonia is a great great house gas. Of course, that would disassociate over time, leaving N2 in the atmosphere.

First, there are asteroids that are pure (or near pure) ammonia. Second, the CFCs are nice, but the ammonia is cheaper and useful afterwards. In particular, the Ammonia starts off as greenhouse gas and then breaks down into pure N2, which then becomes a buffer gas. With CFCs, we would have to import or mine it. As to the water, well, you break up the asteroid just as you hit the atmosphere. Never impacts.

In other news, NASA announced today that a manned mission to Mars is planned to retreive the newly found ice in time for the 2012 Kentucky Derby. NASA plans to upstage Woodford Reserve's famous $1000 Mint Julep at the race with its own $3,000,000 version of the traditional cocktail. While plans are still being firmed up, the beverage will reportedly come in a limited edition collector's glass.

No, martian air is way too dry to form snow. There is water in the athmosphere, but IIRC it is something like a layer 1mm thick if all the water would condense on the ground. What happens is that some of that water freezes to/in the ground if it gets cold enough.

What I learned from following the press conferences online, is that since mars doesn't have a large moon, the axis of rotation changes much more than earth does, so if it is directed towards the sun, the ice could actually melt.

we should wisely remember that all these claims of ice or dry ice and so many other speculations are based on our earthly experience and so are limited to our sense perception. the fact is that every planet, all those millions that you can and cannot see in the sky are fully habitable and many many people are living there. this is the knowledge coming from the topmost intelligent people who have ever appeared on this planet and given fully scientific information about other planets. spending billions on

If I remember my chemistry classes correctly (there is a high chance I don't), water would do this under lower air pressure, I think. Correct me if I'm wrong, I just thought some kind of explanation would be better than "because it's on Mars".

Pretty much anything can sublimate under the proper conditions. But when you say "a white solid that sublimates at -70 degrees F and martian surface pressure and is found in macroscopic quantities naturally" you narrow down the field quite a bit. In this case, to exactly one reasonable possibility.

Pretty much anything can sublimate under the proper conditions. But when you say "a white solid that sublimates at -70 degrees F and martian surface pressure and is found in macroscopic quantities naturally" you narrow down the field quite a bit. In this case, to exactly one reasonable possibility.

To quote wikipedia: This can occur if the atmospheric pressure exerted on the substance is too low to stop the molecules from escaping from the solid state.

Atmospheric pressure is not as important as the partial pressure of the substance at its surface. That is, in this case, the vapour pressure of water which is practically zero on Mars. Therefore water, if it is not locked down in crystalline form, cannot exist in liquid form because it cannot form an equilibrium with its surroundings to form a 'triple point' (solid/liquid/vapour phase temperature).

It also depends, as far as I understand, on the interaction between molecules of the substance. If it is too weak, the range of temperatures at which the substance can be liquid is narrow (or practically zero). It's a fairly wide range for water, though.

All materials sublimate. The liquid phase doesn't exist beneath a substance's triple point, so at pressures beneath that level temperature increases cause the material to go directly from solid to gaseous (sublimate). http://en.wikipedia.org/wiki/Image:Phase-diag2.svga [wikipedia.org] has a good picture of what we're thinking about.

Not sure about helium. If it can sublimate then it's going to be way up the phase diagram at enormous pressure at or close to the critical temperature. But it can definitely go straight from the superfluid state to the vapour state.

It's quite bizarre when you watch He4 transition to superfluid as you reduce the pressure. It's boiling away vigourously and then suddenly all the boiling stops (and it becomes quite difficult to see because it's refractive index is so close to 1)

On earth (at higher pressures), increasing temperature goes from the solid, to liquid, and then to gas phases (the triple-point in the middle is at zero degress celcius)

The lower atmospheric pressure on Mars (~1% of sea-level earth pressure) means that you go straight from solid to gas. In fact, the liquid part is actually impossible (IANAChemist) unless you increase the pressure sufficiently.

water sublimation doesn't need to be exotic; it happens in your freezer all the time.you know how ice cubes gradually lose their sharp edges and finally become just little puddle-shaped lumps in the bottom of the ice try ? that's sublimation too.

Two things I guess. First, the scoop and rasp allows the other tools that they brought like cameras to be used. An auger just creates a small diameter hole in the ground. Second, the auger and any support instruments would probably add considerable power and weight demands to the mission. They don't need that equipment in order to do useful research.

That animation is actually cut off. The main sublimation that was observed is below the frame of that picture. There's a better one here [arizona.edu], where you can actually see the small chunks farther down disappearing completely.

A first glance, it doesn't look to me like ice "melting" any more than salt or some other finely-grained material blowing away (no, I'm not saying it's salt -- just something that could move). Is there no wind in that area or something?

If I understand correctly, the water is blowing away.. just not as crystals. It is blowing away as discreet water molecules much like evaporation. The crystals gain energy from the sun and a little from the impact of the atmospheric gases and then the water molecules lift from the crystal lattice and suspend in the atmospheric gas matrix.

If you visualize everything as tiny versions of the colored balls in a child's play pit, you will notice that each type of ball (atom) has a different weight and tends to

But what about pressure? A look at the phase diagram [wikipedia.org] shows that carbon dioxide can be a solid (dry ice) at 25 C (room temperature), but at 10000 bar. I dunno what the pressure is on the surface of Mars, but temperature isn't the only thing that dictates if dry ice exists. Pressure is just as important. I doubt that Mars has that kind of pressure though.

And why are we using F? This is a science article, posted on a web site for nerds.

I've noticed that almost all of the news headlines covering this are qualified statements like "Lander finds water on Mars, according to scientists". As if they're afraid to actually say something straightforward like "Water found on Mars" and they have to make it clear that they're just reporting what someone else is saying (with the implication that maybe they don't really believe it). At the same time they seem to have no problem with other headlines like "Celebrity Arrested Drunk" without the need to qualify it as "Celebrity Arrested Drunk According To Police" etc.

Maybe it's just me, but I mind it a bit irksome that so many big news outlets seem so detached from any sort of science reporting these days.

I've noticed that almost all of the news headlines covering this are qualified statements like "Lander finds water on Mars, according to scientists". As if they're afraid to actually say something straightforward like "Water found on Mars"

I think the reason is that the scientists technically have no proof it is actually water - what they have instead is a substance that looks like water, behaves like water and quacks like water. Whether it makes said something water, you be the judge.

On the other account, I totally agree - the media don't always seem so scrupulous in other areas:)

Well, as soon as a country from a part of that world, then you'll get your pronouncements to the public in metric. You have to remember that NASA is publicly funded. They need the public engaged in their discoveries, in order to maintain their funding. So, it only makes sense that they report their public findings to the media in units that average ( and the not so average members of congress) understand. I'm sure there are those a NASA that thinks they should be trying to convince the American public to us

Could we have this important information in units used by, I don't know, the rest of the world?

Hah! With this announcement, NASA has predicated that Fahrenheit is now used on the surface of two worlds, thus re-establishing its dominance over that other temperature unit which is only used in part of one world. We will wrest control of this universe back from you metric heathens, even if we have to do it one planet at a time!

You know NASA has made a few major announcements that they have had to retract in the past few years. Remember the "river beds" that had no other possible origin? NASA later admitted that they were likely caused by the wind.

Yes, water ice on Mars is nothing new. That's why they went there. They could not have another failed mission, could they? Before Phoenix there was Opportunity. Why? The NASA-funded mineralogical neophytes spent our money looking for liquid water where they saw widespread hematite...coarse grained grey hematite. Fe2O3...no water in its structure! On Earth, in the banded iron formations that are BILLIONS of years old, that is a metamorphic mineral. It did not form in liquid water! Its PRECURSOR minerals (goethite; ferrihydrite; lepidocrocite) did form in water. Using hematite as a "beacon" for liquid water would be like using anthracite coal as a beacon for a coal swamp or a piece of chinaware as a beacon for a kaolin mine. Now we have a mission that is the equivalent of finding sand in the Sahara Desert? They KNEW that there was water ice there...for years. Big deal? Unbelievable spin! If they actually find anything relevant to life on Mars one needs to inquire... Why didn't they go there in the first place? Why did they waste our money landing in a billion year old metamorphic landscape? Even the face-saving hematite "blueberries" are a joke when placed into context with the remote data used to select that landing site...platy coarse-grained hematite.

First, I think the best evidence so far that this is water is not this picture, but the fact that the Mars Orbiter's spectrometer determined that that is was a lot of hydrogen in the ground near the poles.

That some white stuff vanishes is poor evidence. They need to get the white stuff in an oven and test it.

Let's assume it is water.What really puzzles me is how clean the water is. It is covered with what would make a dirty mud if it ever melted together. Also on earth, you never have clean water if you have flash floods like what you see as a result of a volcanic eruption or meteroid impact. You only have clean water/ice in snow and still lakes/oceans.This implies:1. The ice has not melted after the dust blew over it.(A long time)2. It used to be a lake/ocean or snow

So the purity of the ice might be a bigger discovery than the fact that it is ice there.

there's a number of geological processes that can concentrate water like this

in areas on earth where a lot of freezing and thawing occurs on earth, rocks get concentrated neatly in rings according to size, as if someone sorted them

i'm not saying this process is anything like why the ice is so pure on mars, what i am saying is that there are plenty of natural processes out there that concentrate materials in orders that, contraintuitively, seem like it took intelligent concentration, but are in fact totally natural

i won't even begin to speculate what processes on mars could do this, but i wouldn't be surprised if someone more knowledgeable than me could describe such a natural mechanism for ice purification on mars

So these two frames [spaceweather.com] were taken four days apart while the sublimation was taking place. My question would be - where are the rest of the frames? Does this lander really only "look around" every few days?

It would be nice to see it at even a 1-day resolution and get a 4-frame animation of the process. Those lumps should be seen to get smaller and vanish.

That a lot of the people here see dry ice, white and solid like the stuff found on mars, and the fact that dry ice subliminates in our atmosphere, and come up with the idea that the white stuff must be solid CO2 and not water. Of course this is completely fallacious logic, as the pressure and temp in the area make it physicaly impossible for CO2 to be a solid (if temp/pressure data is correct)....

You say you think it's sublimationWell you knowthat'd be out of this worldWhat else could explain the diminutionWell you knowthat'd be out of this worldBut when you talk about reductionDon't you know ice ain't the only thingDon't you know other substances are white [x3]

You say you got an aqueous solutionWell you knowWe'd all want to see the proofMartians might be liliputianWell you knowLook for them if you can canBut if you want money for space probes that craterAll I can tell you is brother maybe laterLearn how to use metrics first, alright? [x4]

I thought this Wired quote about why the water sublimates on Mars is interesting:

"Just like dry ice does here on Earth, water ice goes from solid to gas when the pressure is below 6.1 millibars and it gets heated (like it does in the Martian sun). It can also go straight from solid to gas above 6.1 millibars when the vapor pressure (amount of water vapor in the air) is low enough. This is because the molecules of water in solid form and gas form are not at equilibrium."

Your joke reveals another truth: the limitations of remote instruments. Countless debates in slashdot threads have been had about human versus robotic space exploration. Many folks argue that robots are just as effective as people. Well, certainly they are more cost-effective, but as this Phoenix episode shows they are certainly NOT more effective in practical terms.

It took many days to determine that the white stuff Phoenix uncovered was ice (and not salt). An astronaut on Mars would have made that determination within seconds.

After looking at that fascinating GIF from the summary, I'm not sure it is water. It just kind of disappears. It's probably some sort of highly advanced life form that can change its shape at will and lives beneath the planet's surface most of the time. It then just came up for a little Martian sunshine and, upon noticing our probe went back to tell its buddies that the Earthlings sent more crap to their planet and that they should expect an invasion soon. Unless they can prove to us they don't have any

It was at the bottom of a trench. Plus, wind doesn't selecticely blow white rocks away while letting the rest of the scene untouched. Plus, you can also see some white areas at the end of the trench getting smaller.

Not only that, but Phoenix has a little weather station on board called the Telltale project [marslab.dk]. And if you look at this page [space.gc.ca] you can see the weather reports for where Phoenix is on a sol by sol basis. None of them show windy conditions, although it looks like there is data missing for a few sols.

Actually I was just being snarky. I guess because I've been hanging around on Pharyngula and FSTDT a lot lately, dealing with the "evolution is just a theory!" and "particle physics proves astrology!" wackos.

It's 1% of Earth's atmospheric pressure. At that point there is no water, only solid and gas. And the sublimation point is a lot lower because of the lower pressure. (Less pressure = less molecules keeping the other molecules tightly packed)

But seriously, this is oversimplified. Water freezes at 0 degrees on Earth, at standard pressure. Furthermore, even when water freezes, there's still water vapor. Really, if you think about it, you can't have the physical states without multiple molecules. Liquids and solids require certain arrangements of multiple molecules. In either case, individual molecules can escape, thus sublimating. The energy from the sun was enough to cause these molecules to escape, even though

Perhaps next mission they should take along some sugar. Put it out and see if it 'sublimates' as well.

Memo to all Enforcers:By order of the Council of Elders, anyone caught consuming the sweet, sweet bait near the robotic invader from the blue planet is to have his gelsacs summarily pierced.Signed,K'Breel

A similar experiment was recently conducted to determine the existence of life in Congress. A large pile of money was left sitting out which sublimated while votes accreted; thereby proving the existence of life in Congress. It is still up for debate how long before intelligent life is found in Congress.